Pentamidine is used for the treatment of Pneumocystis carinii pneumonia, or "PCP". The importance of pentamidine has escalated recently due to the marked increase of patients suffering from PCP. The increase in the afflicted patient population is an unfortunate consequence of the increasing presence of Acquired Immunodeficiency Syndrome ("AIDS"). It is now estimated that approximately 70 percent of AIDS patients contract PCP. Because of the high incidence of PCP in AIDS patients, pentamidine has found utility not only in the treatment of PCP, but also as prophylaxis, in preventing or delaying the initial onset or recurrence of PCP, especially in AIDS patients. Currently, pentamidine is most commonly administered as a therapeutic agent by intravenous infusion and as a prophylactic agent by aerosol dosage.
However, an unfortunate side effect of pentamidine is its toxicity. Some fatalities have been attributed to severe hypotension, hypoglycemia, and cardiac arrhythmias in patients treated with pentamidine. Contrawise, insufficient dosage may result in dissemination of disease beyond the lung, an occurrence of which is associated with a poor prognosis.
Pentamidine is presently in limited use because of cost and toxicity. Therapeutic drug monitoring is not used because of the cost and complexity of the currently available assay techniques which require the extraction of plasma and High Performance Liquid Chromatography analysis. As a result, the toxicity of pentamidine is a significant concern, which is driving the market toward the development of pentamidine substitutes capable of avoiding or minimizing the undesirable side effects associated with the use of pentamidine. Accordingly, it is an object of the present invention to provide new methods of treating Pneumocystis carinii pneumonia.